July 26, 2013

NASA’s twin Van Allen Probes show that particles in the radiation belts surrounding Earth are accelerated by a local kick of energy, helping to explain how these particles reach speeds of 99 percent the speed of light. Scientists have know that something in space accelerated particles in the Van Allen radiation belts to more than 99 percent the speed of light, but they didn’t know what that something was. New results from NASA‘s Van Allen Probes now show that the acceleration energy comes from within the belts themselves.

Particles inside the belts are sped up by local kicks of energy, buffeting the particles to ever faster speeds, much like a perfectly timed push on a moving swing. Knowing the location of the acceleration will help scientists improve space weather predictions, because changes in the radiation belts can be risky for satellites near Earth, and for astronauts travelling through them on the way to the Moon or Mars, for example.

The radiation belts were discovered upon the launch of the very first successful U.S. satellites sent into space, Explorers I and III. It was quickly realized that the belts were some of the most hazardous environments a spacecraft can experient.

Two swaths of particles surrounding Earth called the radiation belts are one of the greatest natural accelerators in the solar system, able to push particles up to 99% the speed of light. The Van Allen Probes launched in August 2012, have now discovered mechanisms behind this acceleration. (Credit: NASA/Goddard /Scientific Visualization Studio).

Most satellite orbits are chosen to duck below the radiation belts or circle outside of them, and some satellites, such as GPS spacecraft, must operate between the two belts. When the belts swell due to incoming space weather, they can encompass these spacecraft, exposing them to dangerous radiation.

A significant number of permanent failures on spacecraft have been caused by radiation. With enough warning, we can protect technology from the worst consequences, but such warning can only be achieved if we truly understand the dynamics of what’s happening inside these mysterious belts.

Scientists believe these new results will lead to better predictions of the complex chain of events that intensify the radiation belts to levels that can disable satellites.

While the work shows that the local energy comes from electromagnetic waves coursing through the belts, it is not known exactly which such waves might be the cause.